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Post by 190mech on Apr 19, 2010 20:37:54 GMT -5
If ya look to the right of the "F" mark in JMStar's photo,youll see 2 other marks,thats where it should be at at Max RPM,the timing should move away from TDC toward the "F" mark."F" should be the idle setting...Need to figure a way to get it there or it'll aways be a TURD!!
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Post by 90GTVert on Apr 19, 2010 20:41:30 GMT -5
I mean I tuned to get the proper main jet. I check plug color, I check max RPM in a given area, and of course seat of the pants. If it's way rich or way lean you can hear it.
It looks like the T is at 0 and the F is at 15 BTDC stock, 17 BTDC now. The max advance I could see was 25 (27 now) BTDC. I could only get to about 5000RPM though. The tire touches the ground so I don't want it to take off on me.
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Post by Fox on Apr 19, 2010 20:47:34 GMT -5
The tire touches the ground so I don't want it to take off on me. Block it up off the ground. Maybe it just needs some break-in time.
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Post by 90GTVert on Apr 19, 2010 20:52:21 GMT -5
The later it gets, the lazier I get. Sorry. I'm probably done with any testing tonight.
It would have to REALLY free up upon break in to be a decent scoot. Once again though, I put more than enough miles on the other setups for them to break in and they never really got any faster.
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Post by 190mech on Apr 20, 2010 4:34:51 GMT -5
A few more,,is TDC really TDC?We talked about cam timing last build,so I'm doing it again.Got any other cams?When its at TDC compression stroke,turn the flywheel 360 degrees.Exhaust valve should be almost closed and intake just opening,do we have this?A degree wheel check of the cam events would tell all,but dont know if the turd is worth it..Back to ign timing,can it be checked while riding?Sounds scary!
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Post by 90GTVert on Apr 20, 2010 5:44:21 GMT -5
I'm not sure how I'd sit on the seat, hold the gas, steer, and aim the timing light at the flywheel? Marks on the flywheel are even looking the wrong direction so you'd have to be a contortionist to do all these things at once. I need a side car and another person. lol It's been like this with 2 crankshafts and 2 cams. I guess if anything was off it'd have to be the flywheel... but then I'm getting basically the right timing specs at idle.
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Post by 2strokd on Apr 20, 2010 7:44:08 GMT -5
It would make a nice mailbox i think ! Sorry man, i couldnt help myself , all shut up....
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Post by 190mech on Apr 20, 2010 11:23:05 GMT -5
Surely we are missing something here,many 139's run well,why doesnt this one??Ignition,compression,cam timing,cvt system,final drive,carb,exhaust,where is the gremlin?
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Post by 190mech on Apr 20, 2010 11:49:55 GMT -5
How about the ignition module?Restricted?
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Post by 90GTVert on Apr 20, 2010 13:08:52 GMT -5
I can't check compression because I have no dinky little fitting that works with these plugs. I really don't think that's the issue. The compression feels pretty strong when I turn the engine over.
I've got the Naraku variator on there. stock belt 669 something, and I've had a complete new rear clutch/pulley on it as well as different rollers, clutch springs, and torque springs..
I've used stock and aftermarket exhausts and it's always slow.
2 cams, 2 cranks. Always slow.
Gearing seems the same as others from Dave's specs.
3 carbs have been used. Always slow.
I replaced the CDI some time ago. It's not RPM restricted. Possibly not enough timing in it's curve though. I got the CDI from Sunl Parts so it could be the exact same as stock with a crap curve.
To make it complete, here is how much stuff I replaced or tried on this scooter since I got it...
Air inlets : stock, 2 UNIs, K&N Carbs : stock, stock modified, 150 Intakes : stock, stock ported, 150 port matched Heads : stock, stock ported, 47mm, 50mm big valve Cylinders : 47mm, 50mm Cranks : stock, stock replacement Cams : stock, NCY Valve springs : stock, NCY 150 Variators : stock, Naraku Rollers : 4g to 10g Belts : stock Clutches : stock, stock replacement Clutch bells : stock, stock replacement Clutch springs : stock, 1500, 2000 Torque drivers : stock, stock replacement Torque springs : stock, 1000, Naraku 1000 (feels stiffer than standard 1000), 1500 Tires : 3.50x 10, 120/90/10 Wiring harnesses : stock, stock replacement with junk removed CDIs : stock, stock replacement Petcocks : stock, manual
I've also replaced some hand controls, the rectifier, headlight, battery, wheel bearings, steering bearings, signal flasher, etc... Point being, I've replaced nearly everything on this scooter. Shore of replacing the cases the entire engine is new.
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Post by 190mech on Apr 20, 2010 14:15:39 GMT -5
Anybody have a known good CDI box from a good running 139 they can send Brent for a test?
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Post by 90GTVert on Apr 20, 2010 14:33:22 GMT -5
I made a vid to show you guys what the timing is doing and so I could see it easier to make sure my numbers are accurate... The ignition pickup is actually installed 3 degrees advanced, I thought it was 2 yesterday. So the T is at 0 degrees (TDC) or at least I hope so. The F is 15 degrees advanced. It looks like timing is advancing only 9 degrees past F (it shows 12, but remember I have to be at 3 degrees advanced to line up with F at idle), for a total of 24 degrees of ignition advance max. It's a bit shy of reaching the marks on the flywheel. Maybe I should go through a known good dealer like Jeremy or Jim of Rapid Repair or something like that and get an advanced or adjustable CDI, or maybe just a known good stocker like John said? On a brighter note, I changed the oil after some running time and maybe 5-10 miles total. Looks clean, no glitter, nothing alarming. Really didn't need to be changed, but I always like to get the oil out quick the first time after a new build.
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Post by 90GTVert on Apr 20, 2010 18:40:38 GMT -5
Just to double check, I stuck the stock CDI back in and took it for a quick ride and it seems exactly the same.
Oh, just another thing I've noticed. Everyone says these are "wasted spark" engines that fire on every revolution like a 2 stroke. I have to set my timing light for 4T though or it doubles the revs, so it must not be a wasted spark style.
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Post by stepthrutuner on Apr 20, 2010 19:51:29 GMT -5
As far as valve timing is concerned all I could find are these figures from this site. auction.netbikes.com.au/vjmw.php?dir=wstiming&page=timingThe article says these are typical. I (with due respect to Jethro Bodine) ciphered the durations and overlap on my own. Inlet opens 26 degrees btdc :2800 intake valve durationInlet closes 74 degrees abdc :570 int/exh overlapExhaust opens 68 degrees bbdc :2790 exhaust valve durationExhaust closes 31 degrees atdc
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Post by 90GTVert on Apr 21, 2010 8:34:51 GMT -5
I got the degree wheel and the dial indicator out, but I don't think there's much need to go past correcting TDC at this point. Here's the degree wheel set at 0 with the flywheel on T, and the piston's position at this point. Then I used a dial indicator to find true TDC. Here's the piston's position and the degree wheel's position, relative to the flywheel at TDC. Looks like it's about 21 degrees off of TDC! Yay, China! Here's actual TDC etched and marked on the flywheel. I could definitely imagine that 21 degrees off could make a big difference in performance. I'm surprised it runs. I have an 8 pole stator here, and this one is a 6 pole. I believe they need different flywheels, so I was considering getting an 8 pole flywheel and up-converting the electrical system and hopefully speeding it up a bit. How's that sound? Scrappy sells the flywheel for only $25. Not that I really wanna spend money right now, but if it fixed the "turdishness" of this then, it could quite possibly be the best $25 I've ever spent. Should I just install the cam in a different position? It seems like if a new flywheel was machined correct, it would make life easier anytime I needed to do work to this engine in the future as opposed to other methods of correction?
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